A method for producing a particle reinforced metal matrix composite having a large difference in density

Abstract

The present application belongs to the field of metal matrix composites, powder metallurgy technology and rapid condensation forming, and more particularly relates to a preparation method of a particle reinforced metal matrix composite with large density difference. First, a composite powder of a reinforcing phase and a base metal is obtained by ball milling, and the composite powder is pre-pressed and formed, and then subjected to spark plasma sintering, so that the particle reinforced phase powder and the base metal powder are rapidly sintered and formed, and the interface of the two phases does not react; after sintering, the pressure is released and the furnace is cooled, and a metal matrix composite mother ingot is obtained; then the metal matrix composite mother ingot is rapidly heated and melted in an inert atmosphere to obtain an alloy melt, so as to remove the pores formed in the sintering process of the metal matrix composite mother ingot, and finally the alloy melt is rapidly cooled to obtain a composite material which is uniformly dispersed, high in density, excellent in mechanical properties and free of air trapping.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of metal matrix composites, powder metallurgy technology and rapid solidification forming, and more particularly relates to a preparation method of a particle reinforced metal matrix composite with large density difference. BACKGROUND

[0002] Compared with traditional metal materials, metal matrix composites can overcome some limitations of single metal, achieve synergistic effect, and have many excellent properties that single-phase materials do not have, such as higher strength and stiffness, excellent wear resistance. Among them, particle reinforced metal matrix composites have high specific stiffness, high specific strength, wear resistance, dimensional stability and other advantages, and more importantly, the particle reinforcement phase is relatively low in price, widely available and relatively simple in preparation process, and it has no orientation in the metal matrix, and an isotropic metal matrix composite can be prepared, which has better mechanical properties. Therefore, particle reinforced metal matrix composites are most widely used and widely used in aerospace, energy engineering, automobile manufacturing, shipbuilding and marine engineering equipment fields.

[0003] Particle reinforced metal matrix composites are a new material with different properties from the matrix, which is obtained by adding or in-situ generating one or several particle reinforcement phases to the pure metal or alloy matrix and combining with the matrix. Among them, there is a composite material with large density difference between the added particles and the metal matrix, which plays a key role in actual production and application. For example, the document "Preparation and Performance Research of Tungsten Particle Reinforced Zirconium-based Amorphous Alloy Composite" prepared a composite material with a density difference of nearly 3 times between tungsten particles and amorphous powder. The high volume fraction of tungsten particles ensures the shear "self-sharpening" of the amorphous alloy while making the amorphous alloy have high strength and certain plasticity, thereby improving the penetration power of the amorphous alloy composite. By adding particles with obvious density difference to the metal matrix, such as ceramic particles or light metal particles, lightweight design can be achieved while maintaining good mechanical properties, which is crucial for fields that require lightweight and high-strength materials. It can also significantly improve the wear resistance and corrosion resistance of the material, and also improve the high-temperature performance of the material. However, the preparation of this kind of two-phase particle reinforced metal matrix composite with obvious density difference has great challenges. During the preparation process, it is difficult to make the reinforcement phase uniformly dispersed in the metal matrix due to the large density difference between the two phases, and the reinforcement phase is prone to serious segregation. Defects such as cracks are easily generated during heat treatment, which leads to a decrease in mechanical properties, and the preparation process is relatively complex and the cost is relatively high.

[0004] Currently, most studies use powder metallurgy, stir casting, 3D printing technology, etc. to prepare two-phase particle reinforced metal matrix composites with obvious density difference. The invention patent CN105401001A discloses a process for preparing tungsten particle reinforced aluminum matrix composite by powder metallurgy. The method of ball milling powder and then hot isostatic pressing and sintering is used to prepare tungsten particle reinforced aluminum matrix composite with large density difference between two phases. However, due to the large density difference between two phases, the powder metallurgy method will cause the uneven distribution of the reinforcing phase in the matrix when preparing such composites. During the sintering process, the uneven distribution of temperature will lead to composition segregation, and the material has low density and certain porosity. For amorphous alloys, the large temperature gradient and the difficulty in accurately controlling the temperature during the sintering process will cause local crystallization of amorphous alloys. Praveen et al. prepared high-entropy alloy particle reinforced 2024Al matrix composites by stir casting process. However, when preparing composites with large density difference between two phases, the sinking of particles with high density during stirring leads to uneven distribution of reinforcing phase. When the volume fraction of reinforcing phase is large, the stirring process is difficult to carry out, and air holes are easily produced in the material during stirring. Due to the heat generated by stirring, the material will be affected at relatively high temperature. The invention patent CN115635077A discloses a preparation method of additive manufacturing ceramic particle reinforced metal matrix composite. The gas atomized metal powder is added to the dispersion liquid containing ceramic powder, stirred until the organic solvent is completely volatilized, and the core-shell structure composite powder is obtained. The core-shell structure composite powder is prepared into ceramic particle reinforced metal matrix composite by selective laser melting. However, during the selective laser melting process, a high-temperature small molten pool is formed, the solidification time is short, and the solidification process is complex. The reinforcing particles are easily decomposed and dissolved, which will affect the properties of the matrix. It is still difficult to control the organization and performance of the particle reinforced metal matrix composite prepared by selective laser melting. In addition, the selective laser melting equipment has high cost, limited forming size and low forming efficiency. In order to overcome the adverse effects of the large density difference between two phases under the gravity of the earth, NASA space amorphous metal manufacturing research focuses on the microstructure of bulk metallic glass and tungsten ball composite materials processed under microgravity. The composite material formed by tungsten and metallic glass creates a new type of high-performance alloy and coating, but the method is difficult to implement and has high cost. SUMMARY

[0005] In view of the defects of the prior art, the purpose of the present application is to provide a preparation method of particle reinforced metal matrix composite with large density difference, to solve the technical problems of the prior art forming method of particle reinforced metal matrix composite with obvious density difference between two phases, such as limitation of particle reinforcing phase density, complex control of composite material density, uneven distribution of particle phase, low forming efficiency and high cost.

[0006] To achieve the above object, the application provides a preparation method of a particle reinforced metal matrix composite material with large density difference, comprising the following steps:

[0007] (1) mixing a particle reinforced phase powder and a matrix metal powder by ball milling to obtain a uniformly mixed composite powder;

[0008] (2) pre-pressing the composite powder obtained in step (1) to form a pre-pressed product, and then performing discharge plasma sintering on the pre-pressed product, so that the particle reinforced phase powder and the matrix metal powder are sintered to form a two-phase sintered product, and no interfacial reaction occurs at the interface between the two phases; after sintering, the pressure is released and the sintered product is cooled in the furnace to obtain a metal matrix composite material mother ingot;

[0009] (3) heating and melting the metal matrix composite material mother ingot obtained in step (2) in an inert atmosphere to obtain an alloy melt, so as to remove the pores formed in the sintering process of the metal matrix composite material mother ingot, and then cooling the alloy melt to obtain the particle reinforced metal matrix composite material with large density difference.

[0010] Preferably, the density difference between the particle reinforced phase powder and the matrix metal powder in step (1) is two times or more, and the volume of the particle reinforced phase accounts for 30-60% of the total volume of the reinforced phase powder and the matrix powder.

[0011] Preferably, the particle reinforced phase is metal particles and / or ceramic particles, the metal particles are one or more of metal elements and metal alloys, the metal alloys are amorphous alloys or high-entropy alloys, and the ceramic particles are one or more of Al2O3, WC and Si3N4.

[0012] The matrix metal is one or more of metal elements and metal alloys.

[0013] Preferably, the average particle size of the reinforced phase powder is 20-100 μm, and the average particle size of the matrix metal powder is 40-80 μm.

[0014] Preferably, the ball milling ratio in step (1) is 5:1-15:1.

[0015] Preferably, the composite powder obtained in step (1) is placed in a sintering mold, and a powder tablet press is used to pre-press the composite powder in step (2).

[0016] Preferably, the particle reinforced phase powder and / or the matrix metal powder is an amorphous alloy, and the discharge plasma sintering process parameters in step (2) include: a sintering temperature of 60-70 ℃, which is lower than or equal to the glass transition temperature of the amorphous alloy, a holding time of 0-10 min, a heating rate of 40-80 K / min, preferably 50-60 K / min; and a sintering pressure of 200-700 MPa.

[0017] The particle reinforced phase powder and the matrix metal powder are not amorphous alloys, and the sintering process parameters of the step (2) include: a sintering temperature of 80-100℃ lower than or equal to the melting point of the phase with lower melting point in the particle reinforced phase powder and the matrix metal powder, a holding time of 0-10min, a heating rate of 40-80K / min, preferably 50-60K / min, and a sintering pressure of 150-600MPa.

[0018] Preferably, the heating melting of the step (3) is rapid heating melting, and the heating process is controlled at a heating rate of 800-1000℃ / s; and the cooling is rapid cooling, and the cooling process is controlled at a cooling rate of 300-400℃ / s.

[0019] Preferably, the heating melting of the step (3) is achieved by vacuum induction melting, and the cooling is achieved by copper mold casting.

[0020] Further preferably, the metal matrix composite ingot is rapidly heated by vacuum induction melting, and the vacuum degree of the vacuum induction furnace is less than or equal to 10 -2 Pa, and the vacuum induction current is controlled at 48-50A; and the pressure difference in the copper mold casting process is 0.5-0.8bar.

[0021] More preferably, the metal matrix composite of the step (3) is prepared by vacuum induction melting copper mold casting process, specifically: the metal matrix composite ingot prepared in the step (2) is placed in a bottom-end-pored casting quartz tube in a vacuum induction furnace, and the alloy is rapidly melted and then held in an inert atmosphere by eddy current heating generated by the inductance coil current, and then the alloy melt is sprayed into the copper mold under the action of the pressure difference to rapidly cool to obtain the metal matrix composite.

[0022] Preferably, the metal matrix composite ingot of the step (2) is rapidly heated and melted in an inert atmosphere to obtain an alloy melt, and the holding time T is determined by the following steps:

[0023] S1: the motion equation of the reinforcing phase particles in the alloy melt is:

[0024]

[0025] Wherein ∑F is the resultant force received by the reinforcing phase particles, G0 is the effective gravity of the reinforcing phase particles, F d is the fluid resistance received by the reinforcing phase particles, m is the mass of the reinforcing phase particles, and u is the motion speed of the reinforcing phase particles at time t;

[0026] Assuming that the reinforcing phase particles are spherical, its mass Effective gravity Fluid resistance Substitute formula (1) to get:

[0027]

[0028] Where d p is the reinforcing phase particle diameter, p p is the reinforcing phase particle density, p is the fluid density of the alloy melt, and ξ is the resistance coefficient of the reinforcing phase particles;

[0029] S2: Assuming that the reinforcing phase particles in the alloy melt are in the laminar flow region, the particle Reynolds number Re < 1, and Thus:

[0030]

[0031] Where, μ is the viscosity of the alloy melt;

[0032] S3: The entire settling process of the reinforcing phase particles in the alloy melt is regarded as uniform speed, so that the velocity u at time t = u0, u0 is the uniform speed, according to formula (1), G0 = F d When, Then:

[0033]

[0034] Substitute formula (3) into (4) to get:

[0035]

[0036] S4: The descending distance of the particle reinforcing phase during the holding process does not exceed S = 1 × 10 -6 m, and the holding time According to the S value and formula (5), the holding time T can be obtained.

[0037] Overall, compared with the prior art, the above technical solutions conceived by the present application have the following

[0038] Advantages:

[0039] (1) The application proposes a preparation method for a composite material with obvious density difference between a particle reinforced phase and a matrix metal phase (the density difference is more than twice), which fully considers the obvious density difference between the added reinforced phase and the matrix and the relatively large volume fraction of the reinforced phase. First, the composite powder of the reinforced phase and the matrix metal is obtained by ball milling, then the composite powder is pre-pressed and formed, and then discharge plasma sintering is performed to rapidly sinter the particle reinforced phase powder and the matrix metal powder into two phases, and the interface of the two phases does not react; after sintering, the pressure is released and the furnace is cooled to obtain a metal matrix composite material mother ingot; then the metal matrix composite material mother ingot is rapidly heated and melted in an inert atmosphere to obtain an alloy melt to remove the pores formed in the sintering process of the metal matrix composite material mother ingot, and finally the alloy melt is rapidly cooled to obtain the particle reinforced metal matrix composite material with large density difference.

[0040] (2) The ball milling powder mixing method proposed by the application is selected according to the characteristics of the reinforced phase and the matrix. When the reinforced phase and the matrix are both crystalline metals, high-energy ball milling is used for powder mixing, which can make the composite powder mixing more uniform; when the reinforced phase or the matrix metal is an amorphous alloy, low-energy ball milling is used to ensure uniform mixing of the composite powder while avoiding temperature rise caused by high speed, which leads to crystallization of the amorphous alloy.

[0041] (3) The preparation method of the particle reinforced metal matrix composite material with obvious density difference proposed in the preferred embodiment of the application combines the discharge plasma sintering technology and the vacuum induction melting copper mold casting technology, fully integrates the advantages of the two technologies, the discharge plasma sintering technology as a new type of powder metallurgy technology with the advantages of rapid, low temperature, energy saving and environmental protection, provides a distributed uniform and relatively dense bulk metal matrix composite material mother ingot for the copper mold casting process, and this rapid forming can effectively avoid the precipitation of high-density particles, but the metal matrix composite material mother ingot obtained by discharge plasma sintering inevitably contains pores; and the vacuum induction melting copper mold casting as a widely used rapid heating melting and rapid condensation technology, the rapid heating melting as a liquid can fill the pores in the metal matrix composite material mother ingot; then rapid cooling under suitable pressure can avoid particle sedimentation and interface reaction, and also solve the problem of material density and mechanical property reduction caused by low sintering temperature and sintering pressure in the discharge plasma sintering, thereby realizing the complementation of the two methods. It is the ingenious combination of the two specific processes that makes the particle reinforced phase and the matrix metal phase with large density difference be able to be compounded to obtain a composite material with uniform dispersion, high density, excellent mechanical properties and no gas generation.

[0042] (4) The preparation method of the two-phase particle reinforced metal matrix composite material with obvious density difference provided by the application ingeniously combines the spark plasma sintering technology and the vacuum induction melting copper mold casting technology, avoiding the defects existing in the preparation of the two-phase particle reinforced metal matrix composite material with obvious density difference by using one technology. If the vacuum induction melting copper mold casting method is directly used, the powder is easy to splash and be lost during the melting process, and due to the obvious density difference between the reinforcing phase and the matrix and the large volume fraction, the mixture is not uniform and the low-melting-point components volatilize, and the casting process needs to be completed by increasing the pressure difference, resulting in the generation of pores in the composite material. In the present application, the spark plasma sintering technology is first used to prepare the metal matrix composite material ingot. In the spark plasma sintering process, the spark plasma generated by the direct current pulse current passing through the electrode makes the particles in the sintered body generate Joule heat and activate the particle surface, and the particles are consolidated and formed, effectively solving the problems existing in the preparation of the two-phase particle reinforced metal matrix composite material with obvious density difference and large volume fraction of the reinforcing phase by the vacuum induction melting copper mold casting method. However, the temperature in the spark plasma sintering process is difficult to accurately control, and local overheating may occur, which is difficult to control the local crystallization of amorphous metal, and it is also difficult to control the sintering pressure and sintering temperature to obtain a particle reinforced metal matrix composite material with high density and excellent mechanical properties. Therefore, the sintering temperature and sintering pressure are appropriately reduced in the present application, the two-phase uniformly distributed metal matrix composite material ingot is obtained, the interface reaction and crystallization of amorphous metal are avoided, and the vacuum induction melting copper mold casting process is used after the spark plasma sintering to realize the rapid cooling forming of the ingot prepared by the spark plasma sintering, without air entrapment under the appropriate casting pressure, and the problems of material porosity and density reduction caused by the reduction of sintering temperature and sintering pressure during the spark plasma sintering are solved. At the same time, this rapid forming can avoid the deposition of particles with high density. The organic combination of the spark plasma sintering technology and the copper mold casting technology makes it possible to prepare the two-phase particle reinforced metal matrix composite material with obvious density difference, and the preparation method can obtain a metal matrix composite material with high density, easy to control and good mechanical properties.

[0043] (5) Traditional powder metallurgy technology can be used to prepare bulk metal matrix composite material master ingots from composite powders of reinforcing phase powder and metal powder. Currently, the main methods are vacuum hot pressing sintering and hot isostatic pressing sintering. However, these two methods have problems such as slow temperature rise rate, long sintering time and low production efficiency, which easily lead to the deposition of high-density particles, resulting in uneven distribution of reinforcing phase. When the reinforcing phase or matrix is ​​an amorphous alloy, these two methods are only suitable for preparing amorphous alloy systems with a wide supercooled liquid phase region. At the same time, the slow temperature rise rate and uneven heating inside and outside the powder can easily lead to amorphous crystallization, resulting in structural inhomogeneity of the amorphous alloy. In contrast, this invention uses spark plasma sintering to prepare master ingots of particle-reinforced metal matrix composite materials with significant differences in the density of the two phases. Spark plasma sintering is a new rapid sintering technology that directly passes pulse current between powder particles for heating and sintering. It has the advantages of fast temperature rise rate, short sintering time, low sintering temperature and high production efficiency, effectively solving the problems of slow temperature rise rate, uneven powder heating and high-density particle deposition in the traditional powder metallurgy preparation process.

[0044] (6) The present invention uses a vacuum induction melting copper mold spray casting method for the final forming of composite materials. This method achieves rapid melting and rapid solidification. First, the composite material ingot melts rapidly under the action of eddy current generated by the induced current, avoiding the deposition of high-density particles during the melting process. Then, under the action of an appropriate pressure difference, the alloy liquid is sprayed from the quartz tube nozzle into the copper mold directly below for rapid cooling, further avoiding the deposition of high-density particles, and obtaining a particle-reinforced metal matrix composite material with uniform distribution of reinforcing phase, no pores, higher density and better mechanical properties.

[0045] (7) The present invention proposes a method for preparing particle-reinforced metal matrix composites with significant two-phase density differences. This method combines spark plasma sintering technology and vacuum induction melting copper mold spraying technology, overcoming the limitations of traditional preparation methods such as powder metallurgy and stirred casting, which suffer from uneven distribution of reinforcing phases when preparing particle-reinforced metal matrix composites with significant two-phase density differences. It also overcomes the limitations of 3D printing, such as the easy decomposition and dissolution of reinforcing particles affecting matrix properties and the difficulty in controlling the microstructure and properties of composite materials. Furthermore, it solves the problems of complex preparation process and high cost in preparing particle-reinforced metal matrix composites with significant two-phase density differences under microgravity conditions in space. The present invention achieves the preparation of particle-reinforced metal matrix composites with significant two-phase density differences, while possessing a simple preparation method and low production cost.

[0046] (8) The present application combines the spark plasma sintering and vacuum induction melting copper mold casting process to prepare the particle reinforced metal matrix composite material with large density difference and excellent density, compactness and mechanical properties, and is not a simple combination, but particularly reduces the sintering temperature and sintering pressure of the spark plasma sintering process relative to the traditional spark plasma sintering technology, so as to avoid the reaction of the two-phase interface and the crystallization of the amorphous alloy; then the holding time of the vacuum induction melting is specially controlled, so that the reinforcing phase particles in the alloy melt after melting cannot be deposited, thereby ensuring that the obtained composite material is uniformly distributed and has excellent performance.

[0047] (9) The present application combines the spark plasma sintering and vacuum induction melting copper mold casting process to prepare the particle reinforced metal matrix composite material with large density difference and excellent density, compactness and mechanical properties, and is not a simple combination, but particularly reduces the sintering temperature and sintering pressure of the spark plasma sintering process relative to the traditional spark plasma sintering technology, so as to avoid the reaction of the two-phase interface and the crystallization of the amorphous alloy; then the holding time of the vacuum induction melting is specially controlled, so that the reinforcing phase particles in the alloy melt after melting cannot be deposited, thereby ensuring that the obtained composite material is uniformly distributed and has excellent performance. BRIEF DESCRIPTION OF DRAWINGS

[0048] Figure 1 The flowchart for preparing the particle reinforced metal matrix composite material with large density difference according to the present application. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application is further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0050] The prior art has great challenges in preparing metal matrix composites with obvious density difference between two phases and large volume fraction of reinforcing phase. In the preparation process, it is difficult to make the reinforcing phase uniformly disperse in the metal matrix due to the large density difference between two phases, and the reinforcing phase is prone to serious segregation. Defects such as cracks are prone to occur during heat treatment, which leads to the decrease of mechanical properties. At the same time, the preparation process is relatively complex and the cost is relatively high. At present, most studies use powder metallurgy, stirring casting method, 3D printing technology and other methods to prepare particle reinforced metal matrix composites with obvious density difference between two phases, but each method has many limitations and requirements for the type and properties of the material. Therefore, the present application provides a preparation method of particle reinforced metal matrix composite, which fully considers the characteristics of the particle reinforcing phase and the characteristics and specific needs of the metal matrix composite, and improves and designs the existing forming method of the particle reinforced metal matrix composite, so as to obtain a preparation method of particle reinforced metal matrix composite with obvious density difference between two phases, large volume fraction of reinforcing phase and uniform distribution. At the same time, the preparation method can realize high density and easy control of the particle reinforced metal matrix composite with obvious density difference, and the preparation method is simple, high in forming efficiency and low in preparation cost, thereby solving the technical problems of the particle reinforced metal matrix composite forming method in the prior art, such as density limitation of the particle reinforcing phase, complex control of the density of the composite material, uneven distribution of the particle phase, and low forming efficiency and high cost.

[0051] The present application provides a preparation method of particle reinforced metal matrix composite with large density difference between reinforcing phase and matrix, as shown in Figure 1 The present application provides a preparation method of particle reinforced metal matrix composite with large density difference between reinforcing phase and matrix, as shown in

[0052] (1) Ball milling the particle reinforcing phase powder and the matrix metal powder to obtain uniformly mixed composite powder;

[0053] (2) Pre-pressing the composite powder obtained in step (1) to form a pre-pressed product, and then performing spark plasma sintering on the pre-pressed product to sinter the particle reinforcing phase powder and the matrix metal powder into two phases, and the interface between the two phases does not react; after sintering, the pressure is released and the furnace is cooled to obtain a metal matrix composite mother ingot;

[0054] (3) Heating and melting the metal matrix composite mother ingot obtained in step (2) in an inert atmosphere to obtain an alloy melt, so as to remove the pores formed in the sintering process of the metal matrix composite mother ingot, and then cooling the alloy melt to obtain the particle reinforced metal matrix composite with large density difference.

[0055] The density difference between the particle reinforcing phase powder and the matrix metal powder in step (1) is two times or more, and the particle reinforcing phase has a high volume fraction. In some embodiments, the volume fraction of the particle reinforcing phase accounts for 30% to 60% of the total volume of the reinforcing phase powder and the matrix powder.

[0056] The specific materials of the particle-reinforcing phase powder and the matrix metal powder of this invention are not limited, as long as their density difference is two times or more, the preparation method of this invention is applicable. In some embodiments, the particle-reinforcing phase powder can be metal particles (including but not limited to elemental metals or metal alloys, including amorphous alloys and high-entropy alloys), ceramic particles (including but not limited to Al2O3, WC, Si3N4, etc.), etc. Elemental metals as particle-reinforcing phases include W, Ti, Cu, etc., and amorphous alloys include (Fe... 0.76 B 0.1 Si 0.09 P 0.05 ) 99 Ni1, Zr 48 Cu 34 Ag8Al8Pb2, etc., and high-entropy alloys such as AlCoCrFeNi, CrFeNiTaMoV, etc.

[0057] The matrix metal powder is a metallic element or its alloy, including amorphous alloys or high-entropy alloys. Examples of metallic elements used as matrix metals include Cu and Ni, while examples of metallic alloys include 7075Al and AZ31B. Amorphous alloys include Zr. 55 Cu 30 Al 10 Ni5, Zr 52.5 Ti5Cu 17.9 Ni 14.6 Al 10 High-entropy alloys, such as CoCrFeMnNi and AlCoCrFeNi, are examples.

[0058] In some embodiments, when the reinforcing phase powder or matrix metal powder is an amorphous alloy, the selection criteria for the amorphous alloy are: ① strong amorphous forming ability, i.e., the critical amorphous forming size of the amorphous alloy is not less than 15 mm; ② good thermal stability, i.e., the width of the supercooled liquid phase region ΔT > 50 K, where ΔT = T x -T g T g T is the glass transition temperature. x ③ Excellent thermoplastic forming properties, i.e., thermoplastic forming capacity index S > 0.15, where S = ΔT x / (T L -T g ), T L This is the liquidus temperature.

[0059] In some embodiments, both the reinforcing phase powder and the matrix metal powder are prepared by vacuum atomization. The average particle size of the reinforcing phase powder is 20–100 μm, and the average particle size of the matrix metal powder is 40–80 μm.

[0060] In some embodiments, the ball milling in step (1) is performed with a ball-to-powder ratio of 5:1 to 15:1.

[0061] In some embodiments, the powder of the particulate reinforcing phase and the powder of the matrix metal in step (1) are put into a ball milling tank, stainless steel balls are added according to a ball-to-powder ratio, a small amount of alcohol is added as a process control agent to prevent the powder from sticking to the tank, and a full-planet ball mill is used to ball mill to obtain a uniformly mixed composite powder. When the reinforcing phase and the matrix are both crystalline metals, high-energy ball milling is used to mix the powder, and the effective ball milling time is 1.5-2.5 hours, with 4-6 minutes of forward rotation, 1-3 minutes of stopping, and 4-6 minutes of reverse rotation. When the reinforcing phase or the matrix metal is an amorphous alloy, low-energy ball milling is used, and the effective ball milling time is 2-4 hours, with 8-12 minutes of forward rotation, 0.5-1.5 minutes of stopping, and 8-12 minutes of reverse rotation. The stopping time is used to prevent the temperature from being too high.

[0062] In some embodiments, the composite powder obtained in step (1) is placed in a sintering mold in step (2), and a powder tablet press is used to pre-press the composite powder. In preferred embodiments, the sintering mold is made of QRO90 hard alloy material, and the pressing head is made in a stepped shape to increase the maximum pressure that the mold can withstand.

[0063] In some embodiments, the composite powder obtained in step (1) is placed in a sintering mold in step (2), graphite paper is used to separate the contact surface between the mold and the powder for easy demolding, a powder tablet press is used to pre-press the powder, the mold is then placed in a spark plasma sintering furnace, and a suitable sintering process is selected for sintering. After sintering, the pressure is released and the furnace is cooled to obtain a metal matrix composite master ingot. In preferred embodiments, the graphite paper has a thickness of 0.15-0.25 mm. The pre-pressing size is 8-12 Pa.

[0064] In some embodiments, the powder of the particulate reinforcing phase and / or the powder of the matrix metal is an amorphous alloy, and the spark plasma sintering process parameters in step (2) include a sintering temperature of 60-70°C below the glass transition temperature of the amorphous alloy, a holding time of 0-10 minutes, a heating rate of 40-80 K / min, and preferably 50-60 K / min, and a sintering pressure of 200-700 MPa.

[0065] In some embodiments, neither the particulate reinforced phase powder nor the matrix metal powder is an amorphous alloy, and the sintering process parameters of step (2) include: a sintering temperature of 80-100°C lower than or equal to the melting point of the phase with lower melting point among the particulate reinforced phase powder and the matrix metal powder, in some embodiments, the sintering temperature is 300-800°C, a holding time of 0-10 min, a heating rate of 40-80 K / min, preferably 50-60 K / min, and a sintering pressure of 150-600 MPa.

[0066] Compared with the conventional spark plasma sintering technology, the main purpose of the present application is to obtain a two-phase mixed homogeneous master ingot, without considering the influence of sintering process parameters on the performance of the two-phase composite material. The present application particularly reduces the sintering process parameters, including the sintering temperature and the sintering pressure, to avoid the reaction at the two-phase interface, and to avoid the crystallization of the amorphous alloy. For example, for the case that either the particulate reinforced phase or the matrix metal phase is amorphous, the conventional amorphous plasma sintering temperature is 10-20°C lower than the glass transition temperature of the amorphous alloy, while the sintering temperature of the present application is 60-70°C lower than or equal to the glass transition temperature of the amorphous alloy, and the sintering pressure is more than 50 MPa lower than the conventional amorphous plasma sintering pressure. For the case that neither the particulate reinforced phase nor the matrix metal phase is amorphous, the conventional plasma sintering temperature is generally 20-30°C lower than the melting point, while the sintering temperature of the present application is 80-100°C lower than the melting point of the phase with lower melting point among the particulate reinforced phase powder and the matrix metal powder, and the sintering pressure is more than 100 MPa lower than the conventional plasma sintering pressure.

[0067] In preferred embodiments, the heating and melting of step (3) is rapid heating and melting, with a heating rate controlled within 800-1000°C / s during the heating process; and the cooling is rapid cooling, with a cooling rate controlled within 300-400°C / s during the cooling process, to ensure that the particles do not settle and the two-phase interface does not react.

[0068] In some embodiments, the heating and melting of step (3) is achieved by vacuum induction melting, and the cooling is achieved by copper mold casting.

[0069] The rapid heating and melting of step (3) can be achieved by induction melting, laser melting, etc., but considering that the energy density of laser melting is too high and is limited to a small area, induction melting, such as vacuum induction melting, is preferred. In preferred embodiments, the metal matrix composite master ingot is rapidly heated by vacuum induction melting, and the vacuum degree of the vacuum induction furnace is less than or equal to 10 -2Pa, the inert atmosphere is high-purity argon; the inductive coil current should be controlled in the range in which the alloy can be completely melted, the molten metal can be seen to be shiny and obvious rotation of the molten metal can be observed, in some embodiments, the inductive coil current is controlled in the range of 48-50 A.

[0070] The rapid cooling in step (3) can adopt mold cooling technology, atomization technology or surface melting and deposition technology, but considering that the atomization technology is used for powder preparation and the surface melting and deposition technology is mainly used for surface forming, the mold cooling technology is preferably adopted. In some embodiments, the alloy melt is rapidly cooled to obtain the particle reinforced metal matrix composite material with large density difference by using copper mold casting method under the action of pressure difference. The pressure difference is not less than 0.5 bar, so that the alloy melt in the casting test tube is rapidly sprayed into the copper mold to rapidly cool and solidify, and the pressure difference should be controlled in the range of 0.5-0.8 bar. If the pressure difference is too small, the alloy melt cannot be smoothly sprayed into the copper mold due to the viscosity of the alloy melt. If the pressure difference is too large, the speed of the alloy melt sprayed into the copper mold is too fast, and gas rolling and other phenomena can occur.

[0071] In a preferred embodiment, the metal matrix composite material is prepared by using vacuum induction melting copper mold casting process in step (3), specifically, the metal matrix composite material ingot prepared in step (2) is placed in a vacuum induction furnace, a small hole is formed at the bottom of a casting quartz tube, the alloy is rapidly melted and then kept warm in an inert atmosphere by eddy current heating generated by the inductive coil current, and the alloy melt is sprayed into the copper mold under the action of pressure difference to rapidly cool and obtain the metal matrix composite material.

[0072] In some embodiments, the alloy melt is obtained by rapidly heating and melting the metal matrix composite material ingot in step (2) in an inert atmosphere, and the alloy melt is kept warm, and the determination of the keeping warm time T includes the following steps:

[0073] S1: the motion equation of the reinforcing phase particles in the alloy melt is:

[0074]

[0075] wherein ∑F is the resultant force received by the reinforcing phase particles, G0 is the effective gravity of the reinforcing phase particles, F d is the fluid resistance received by the reinforcing phase particles, m is the mass of the reinforcing phase particles, and u is the motion speed of the reinforcing phase particles at time t;

[0076] It is assumed that the reinforcing phase particles are spherical, and the mass effective gravity fluid resistance Substituting formula (1) obtains:

[0077]

[0078] where d p is the diameter of the reinforcing phase particle, p p is the density of the reinforcing phase particle, p is the fluid density of the alloy melt, and ξ is the drag coefficient experienced by the reinforcing phase particle;

[0079] S2: Assuming that the reinforcing phase particle is located in the laminar flow region, its particle Reynolds number Re < 1, and Thus, we have:

[0080]

[0081] where μ is the viscosity of the alloy melt;

[0082] S3: The entire settling process of the reinforcing phase particle in the alloy melt is regarded as uniform velocity, so at time t, its velocity u = u0, u0 is the uniform velocity, according to formula (1), G0 = F d at this time, then:

[0083]

[0084] Substituting formula (3) into (4) gives:

[0085]

[0086] S4: The descending distance of the particle reinforcing phase during the holding process does not exceed S = 1 × 10 -6 m, and the holding time According to the S value and formula (5), the holding time T can be obtained.

[0087] The present invention provides a method for preparing a particle-reinforced metal matrix composite material with significant two-phase density difference, comprising the following steps: (1) weighing a certain amount of particle-reinforced phase powder and matrix metal powder in a suitable proportion and pouring them into a stainless steel ball milling jar, adding an appropriate proportion of stainless steel balls, and then placing the ball milling jar after introducing Ar into an all-round planetary ball mill for ball milling to obtain a composite powder with uniform particle phase distribution; (2) loading the composite powder into a hard alloy mold, and then using a powder press to pre-press the powder, and then placing the mold into a spark plasma sintering furnace, and after sintering, depressurizing and cooling with the furnace to obtain a master ingot of the particle-reinforced metal matrix composite material; (3) cutting the master ingot to obtain a sample of a suitable size, placing it in a quartz tube with a small hole at the bottom, and placing it in a vacuum induction furnace, where it is rapidly melted under the action of induced current, and under the action of an appropriate pressure difference, the alloy liquid is sprayed from the nozzle of the quartz tube into the copper mold directly below for rapid cooling to obtain the desired particle-reinforced metal matrix composite material. This invention employs a composite forming method combining spark plasma sintering and induction melting copper mold spraying, which can prepare particle-reinforced metal matrix composites with significant differences in the density of the two phases, high and uniform content of the particle phase, high density, and excellent mechanical properties.

[0088] The following are specific examples:

[0089] Example 1

[0090] A tungsten-particle-reinforced zirconium-based amorphous alloy composite material with a tungsten volume fraction of 50% was prepared. Tungsten powder and Zr... 55 Cu 30 Al 10 Ni5 amorphous alloy powders were all prepared by vacuum atomization. The average particle size of the tungsten powder was 30 μm. Zr 55 Cu 30 Al 10 The average particle size of Ni5 amorphous alloy powder is 50 μm. Zr 55 Cu 30 Al 10 The critical formation size of Ni5 amorphous alloy is greater than 20 mm, and its glass transition temperature T g The initial crystallization temperature is 683 K, and the initial crystallization temperature is T. x It is 769K, and the liquidus temperature T x The K value is 1165 K, and the width of the supercooled liquid phase region is ΔT = T. x -T g =86K, S=0.178>0.15, exhibiting good thermoplastic forming ability. The target sample size is a cylindrical specimen with a diameter of 5mm and a height of 15mm. The method for preparing this target tungsten particle-reinforced zirconium-based amorphous alloy composite material includes the following steps:

[0091] Step (1): Low-energy ball milling to obtain a uniformly mixed composite powder.

[0092] First, the weighed 150 g of pure tungsten powder and Zr 55 Cu 30 Al 10 Ni5 amorphous alloy powder into a vacuum stainless steel tank, according to the ball ratio 10:1 to add 1500 g of stainless steel ball, in order to prevent the powder tank, add 10 ml of alcohol as a process control agent, then the tank is vacuum, the tank is tightly installed in the ball mill;

[0093] The use of all-terrain planetary ball mill, using lower speed 200 r / min for mixing powder, 10 min after the positive stop 1 min and then reverse 10 min, set the effective ball milling powder time is 3 h, after the ball milling to take out the composite powder.

[0094] Step (2): spark plasma sintering preparation of granular phase distribution uniform composite ingot

[0095] The mixed powder in step (1) is loaded into the mold made of QRO90 hard alloy material for sintering, the inner diameter of the mold cavity is Φ = 15.4 mm, and the diameter of the pressure head is Φ = 15 mm. In order to facilitate demolding, graphite paper is used to separate the contact surface between the mold and the powder. In addition to using graphite paper around, graphite paper is also used on top and bottom, and the thickness of the graphite paper is 0.2 mm.

[0096] After the powder is loaded, a small powder tablet press is used to pre-press the powder at about 10 Pa, and then the mold is placed in the spark plasma sintering furnace. The sintering temperature is 621 K, the holding time is 2 min, the heating rate is 50 K / min, and the sintering pressure is 300 MPa. After sintering, the pressure is released and the furnace is cooled to obtain an amorphous alloy composite ingot.

[0097] Step (3): copper mold spray casting by vacuum induction melting

[0098] After the amorphous alloy composite ingot obtained by sintering in step (2) is cut into a size of 4 × 4 × 4 mm, it is placed in a quartz tube with a small hole of 1.6 mm in diameter at the bottom end, and is placed in a vacuum induction furnace. After repeatedly washing with argon gas, vacuum is achieved to 3.5 × 10 -3 Pa, and appropriate argon gas is filled. In a high-purity argon atmosphere, the alloy is rapidly melted by eddy current heating generated by an induction coil. The maximum heating current is 48 A, and the holding time is calculated according to formula (5), where the tungsten particle diameter d p = 30 μm, the tungsten particle density ρ p = 19.35 g / cm 3 , Zr 55 Cu 30 Al 10Density of Ni5 fluid p = 6.55 g / cm 3 Fluid viscosity μ ~ 1 x 10 4 Pa-s, substituting into equation (5) gives: sedimentation velocity Therefore, the holding time And under the action of pressure difference of 0.7 bar, alloy melt is sprayed into copper mold for rapid cooling, and the amorphous alloy composite rod with diameter of 5 mm is obtained by spray casting, that is, the tungsten particle reinforced zirconium-based amorphous alloy composite material with tungsten volume fraction of 50%.

[0099] Example 2

[0100] A WC particle reinforced aluminum-based composite material with a WC volume fraction of 40% is prepared. The WC powder and the 7075 Al powder are both prepared by vacuum gas atomization method, the average particle size of the WC powder is 50 μm, and the average particle size of the 7075 Al powder is 60 μm. The target sample size is a cylindrical sample with a diameter of 5 mm and a height of 15 mm. The method for preparing the target WC particle reinforced aluminum-based composite material comprises the following steps:

[0101] Step (1): high-energy ball milling to obtain uniformly mixed composite powder

[0102] First, weigh 150 g of WC powder and 7075 Al powder into a vacuum stainless steel tank, add 1500 g of stainless steel balls according to the ball-to-powder ratio of 10:1, and add 10 ml of alcohol as a process control agent to prevent the powder from sticking to the tank. Then, the steel tank is tightly installed in the ball mill after being evacuated.

[0103] A full-planet ball mill is used for ball milling, and a higher speed of 800 r / min is used for powder mixing. After 5 minutes of forward rotation, it is stopped for 2 minutes and then reversed for 5 minutes. The effective ball milling and powder mixing time is set to 2 hours. After the ball milling is completed, the composite powder is taken out.

[0104] Step (2): spark plasma sintering to prepare a composite material master ingot with uniform particle phase distribution

[0105] The well-mixed powder in step (1) is loaded into a mold made of QRO90 hard alloy material for sintering, and the inner diameter of the mold cavity is Φ = 15.4 mm, and the diameter of the pressure head is Φ = 15 mm. In order to facilitate demolding, graphite paper is used to separate the contact surface between the mold and the powder. In addition to using graphite paper around, graphite paper is also used on top and bottom, and the thickness of the graphite paper is 0.2 mm.

[0106] After the powder is filled, the powder is pre-pressed by a small powder tablet press at about 10 Pa, and then the mold is placed in a spark plasma sintering furnace, the sintering temperature is 683 K, the holding time is 8 min, the heating rate is 50 K / min, the sintering pressure is 200 MPa, and after sintering, the pressure is released and the furnace is cooled to obtain an aluminum-based composite material mother ingot.

[0107] Step (3): forming by vacuum induction melting copper mold injection casting

[0108] The amorphous alloy composite material mother ingot obtained by sintering in step (2) is cut into a size of 4x4x4 mm and placed in a quartz tube with a small hole of 1.6 mm in diameter at the bottom, and then placed in a vacuum induction furnace, and repeatedly argon gas is filled and vacuumized to reach a vacuum degree of 3.5x10 -3 Pa, and appropriate argon gas is filled. In a high-purity argon atmosphere, the alloy is rapidly melted by eddy current heating generated by an induction coil, the maximum heating current is 50 A, and the holding time is calculated according to formula (5), wherein the WC particle diameter d p = 50 μm, the WC particle density ρ p = 15.63 g / cm 3 , the density of 7075 Al fluid ρ = 2.81 g / cm 3 , the fluid viscosity μ ≈ 8x10 3 Pa·s, and formula (5) is substituted to obtain the settling velocity Therefore, the holding time Under the action of a pressure difference of 0.6 bar, the alloy melt is sprayed into the copper mold for rapid cooling, and an aluminum-based composite material rod with a diameter of 5 mm is obtained by injection casting, which is the WC particle reinforced aluminum-based composite material with a WC volume fraction of 50%.

[0109] Those skilled in the art will readily understand that the above description is only a preferred embodiment of the present application and is not intended to limit the present application, and any modifications, equivalent replacements and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method of producing a particulate reinforced metal matrix composite material having a large difference in density, characterized by, The method comprises the following steps: (1) ball-milling the particle reinforced phase powder and the matrix metal powder to obtain a uniformly mixed composite powder; (2) pre-pressing the composite powder obtained in step (1) to form a pre-pressed product, and then performing spark plasma sintering on the pre-pressed product to sinter the particle reinforced phase powder and the matrix metal powder into two phases, and the interface between the two phases does not react; after sintering, the pressure is released and the sintered product is cooled in the furnace to obtain a metal matrix composite material ingot; (3) heating and melting the metal matrix composite material ingot obtained in step (2) in an inert atmosphere to obtain an alloy melt, and then performing heat preservation to remove the pores formed in the sintering process of the metal matrix composite material ingot, and then cooling the alloy melt to obtain the particle reinforced metal matrix composite material with large density difference; wherein said holding its holding time T The determination includes the following steps: S1: the motion equation of the reinforced phase particles in the alloy melt is: wherein is the resultant force on the reinforcing phase particles, is the effective gravity on the reinforcing phase particles, is the fluid drag force on the reinforcing phase particles, is the mass of the reinforcing phase particles, is the velocity of the reinforcing phase particles at time t; Assuming that the reinforcing phase particles are spherical, their mass , effective gravity , fluid drag , into equation (1) gives: wherein for the reinforcing phase particle diameter, for the reinforcing phase particle density, for the fluid density of the alloy melt, for the drag coefficient experienced by the reinforcing phase particle; S2: Assuming that the reinforcing phase particles in the alloy melt are located in the laminar flow region, the particle Reynolds number and , Thus, we have: wherein μ is the viscosity of the alloy melt; S3: If the entire settling process of the reinforcing phase particles in the alloy melt is regarded as uniform, then at time t its velocity u=u0, u0 is the uniform velocity, according to formula (1). hour, ,but: Substitute formula (3) into (4) to obtain: S4: the falling distance of the particle reinforcing phase during the holding process is not more than 0.5*H its holding time According to the S value and formula (5), the holding time T can be obtained.

2. The production method according to claim 1, wherein The density difference between the particle reinforced phase powder and the matrix metal powder in step (1) is two times or more, and the volume of the particle reinforced phase accounts for 30-60% of the total volume of the reinforced phase powder and the matrix powder.

3. The production method according to claim 1, wherein The particle reinforced phase is metal particles and / or ceramic particles, the metal particles are one or more of metal elements and metal alloys, the metal alloys are amorphous alloys or high-entropy alloys, and the ceramic particles are one or more of Al2O3, WC and Si3N4. The matrix metal is one or more of metal elements and metal alloys.

4. The production method according to claim 1, wherein The average particle size of the reinforced phase powder is 20-100 μm, and the average particle size of the matrix metal powder is 40-80 μm.

5. The production method according to claim 1, wherein The particle reinforced phase powder and / or the matrix metal powder are amorphous alloys, and the spark plasma sintering process parameters in step (2) include: the sintering temperature is 60-70 ℃ lower than the glass transition temperature of the amorphous alloy, the heat preservation time is 0-10 min, the heating rate is 40-80 K / min, and the sintering pressure is 200-700 MPa; or The particle reinforced phase powder and the matrix metal powder are not amorphous alloys, and the spark plasma sintering process parameters in step (2) include: the sintering temperature is 80-100 ℃ lower than the melting point of the phase with lower melting point among the particle reinforced phase powder and the matrix metal powder, the heat preservation time is 0-10 min, the heating rate is 40-80 K / min, and the sintering pressure is 150-600 MPa.

6. The production method according to claim 1, wherein The heating and melting in step (3) is rapid heating and melting, and the heating rate of the heating process is controlled at 800-1000 ℃ / s; the cooling is rapid cooling, and the cooling rate of the cooling process is controlled at 300-400 ℃ / s.

7. The production method according to claim 6, wherein The heating and melting in step (3) is achieved by vacuum induction melting, and the cooling is achieved by copper mold casting.

8. The production method according to claim 7, wherein The metal matrix composite ingot is rapidly heated by vacuum induction melting; the vacuum degree of the vacuum induction furnace is less than or equal to 10 -2 Pa, the vacuum induction current is controlled at 48-50 A; and the pressure difference in the copper mold casting process is 0.5-0.8 bar.

9. The production method according to claim 8, wherein The step (3) is to prepare the metal matrix composite material by a vacuum induction melting copper mold casting process, specifically: the metal matrix composite material ingot prepared in the step (2) is placed in a vacuum induction furnace, and a small hole is arranged at the bottom of a casting quartz tube; in an inert atmosphere, the alloy is rapidly melted by eddy current generated by the current of an induction coil and then is kept warm; then under the action of a pressure difference, the alloy melt is sprayed into a copper mold to rapidly cool to obtain the metal matrix composite material.

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